Crude oil and its derivatives are subjected to a number of processes involving the addition of hydrogen in order to maximize, or upgrade, the distillable fractions to thereby obtain a wide variety of different and more valuable compounds. These processes include hydrocracking, hydrodesulfurization in order to lower the sulfur content of the feedstream and hydrotreating to reduce nitrogen, oxygen and/or metal compounds in the treated stream. In the current practice of these processes, a stream of hydrogen is typically introduced into the treatment vessel where it contacts the feedstream in the presence of one or more catalysts. The hydrogen stream is typically generated in a separate unit or facility, often using natural gas, and then purified, compressed and delivered to the processing vessel. Thus, the cost of hydrocracking, hydrotreating and other such processes must include the capital and operating costs associated with the construction and operation of the unit and/or facilities required to produce the hydrogen stream.
For convenience, the term “hydroprocessing” will be used in this description with the intention that it include any of the other specific methods and processes for treating crude oil and its fractions in which hydrogen is reacted to produce new compounds, typically of lower molecular weight and shorter chain length.
It is well known that hydrogen can be generated electrochemically by dissociation of water molecules to ionic form, i.e., hydrogen atoms, or protons, and oxygen atoms. There is disclosed in U.S. Pat. No. 6,218,556. an electrochemical process for hydrogenating an unsaturated fatty acid, mixtures of two more fatty acids, or the unsaturated fatty acid constituents of an edible or non-edible oil's triglycerides employing a solid polymer electrolyte reactor. In the disclosed process, hydrogen is generated in situ by the electro-reduction of protons that are formed at the anode and then migrate through the ion exchange membrane for reaction. It is stated that only the H+ ions, or protons, carry the electrical current between the anode and cathode thereby circumventing the need for a supporting electrolyte to conduct the electrical current for the process. The method and apparatus of this disclosure is not suitable for use with crude or other heavy mineral oils, since the membrane would be fouled quickly and already has a limited rate of ion transport; also, the membrane apparently has a maximum operating temperature of about 180° C.
A method for generating hydrogen by electrolysis in a subterranean geological formation for the treatment of tar sands is disclosed in U.S. Pat. No. 4,204,923. A typical acid electrolyte is used and the addition of the hydrogen to the petroleum appears to be by absorption. This process does not employ any catalyst or other similar hydroprocessing method.
These disclosures suggest the desirability of a process in which hydrogen is generated via an electrochemical process for use in hydroprocessing of crude oil and its fractions. However, there remains the principal problem of how to bring the hydrogen and the organic molecules of the mineral oil feedstream into contact in order to allow the hydrogenation to take place, e.g., to form an emulsion, that can include foam, while having to then separate the oil and water mixture.
It is therefore an object of the present invention to provide a process and apparatus that will permit the in situ generation of hydrogen atoms by the electrolysis of water molecules which provides for the intimate mixing of the water and hydrocarbon phases during the reaction and then permits the easy separation and recovery of the hydrocarbons from the reaction zone.
Another object of the invention is to provide a method and apparatus for the in situ electrochemical generation of hydrogen atoms, or protons, in the presence of a hydrocarbon feedstream which is subjected to hydroprocessing conditions in order that the hydrogen ions generated can take part in the upgrading reaction on an essentially stoichiometric basis.
It is a further object of the present invention to provide a method in which an ionic material that permits the formation of an intimate mixture of the hydrocarbon feedstream with the electrochemically-generated hydrogen atoms can be easily recovered and recycled for reuse in the process.